For many years coaxial cable has been the transmission medium of choice for high-speed electronic applications. The controlled impedance, low crosstalk and EMI/RFI o (electromagnetic interference/radiofrequency interference) shielding offered by coaxial cable are the driving forces for its selection for such applications. The sophistication and speed of electronic instrumentation and equipment has increased significantly in recent years due to the rapid advances in the capabilities of microprocessor technology in both speed and density. Connectors and interconnections for such equipment, and in particular, for coaxial cable, have seen similar increases in pin count and density requirements.
In the high-speed electronic applications requiring coaxial cable the interconnection scheme must maintain acceptable levels of signal integrity, particularly with respect to crosstalk, shielding and controlled impedance. Providing this performance requires that the connector introduces minimal effects on the consistency of the impedance and shielding of the cable through the connector and across the separable interface. One approach to meeting this requirement at increased connector density is to use microcoaxial cable, with center conductors of 40 AWG and smaller. Processing coaxial cable elements with outside diameters of less than 0.5 mm, and center conductors of 0.075 mm, and smaller, present design and manufacturing challenges.
To facilitate cable preparation a microferrule process has been developed and is disclosed in U.S. Pat. No. 5,061,827. A thin copper foil is applied around the outside of the cable, exposing the shield wires along the axis of the foil by laser ablation, and soldering the shield wires directly to the foil. The copper foil strip is sheared and formed to suitable dimensions to define, in one embodiment, axially extending barbed edges which when the foil is disposed around the cable will oppose each other and will extend radially inwardly to penetrate the outer insulation of the coaxial elements and engage the shield wires. The partially formed microferrule is transferred into a nest which is transferred beneath and in axial alignment with the coaxial element, after which the microferrule is crimped onto the coaxial element. Upon crimping the microferrule defines an open seam between the radial locations of insulation penetration by the barbed edges, exposing the cable insulation for ablation to expose the shield wires to be soldered to the microferrule through reflow soldering using solder paste deposited thereat, all using a CO.sub.2 laser system, RF modulated 25 watt, sealed, in conjunction with a PC-based TTL pulse generator to attain the extremely different pulse definitions for the two tasks. Thereafter the insulation forwardly of the crimp area is stripped through conventional mechanical or laser methods, to expose the inner dielectric and center conductor for termination.
It is desired to provide a connector capable of accepting sixteen coaxial elements in a microstrip configuration, where the modular connector serves as an electrical bridge between the coaxial elements and a printed wiring board. U.S. Pat. No. 4,927,369 discloses an interposer connection assembly for interconnecting such a modular connector having a printed circuit element mounted to the mating face, to a printed wiring board.
It is additionally desired that such connector accommodate a plurality of microcoaxial elements in a very closely spaced, or high density, configuration for both the signal and ground conductors thereof.
It is also desired that such a high density connector be easily applied in a simplified procedure, with automatic controlled soldering of the signal conductors to respective contacts when in the connector housing.